Glossary of River Terminology

Ablation - The process by which ice and snow waste away as a result
of melting and/or evaporation.

Abrasion - Removal of stream-bank soil as a result of sediment-laden
water, ice, or debris rubbing against the bank.

Acid rain - Rainfall with a pH of less than 5.7. Long-term deposition
of these acids is linked to adverse effects on aquatic organisms and plant
life in areas with poor neutralizing (buffering) capacity.

Acidic - The condition of water or soil in which the amount of acid
substances are sufficient to lower the pH below 7.0.

Acre-foot (af) - A quantity or volume of water covering 1 acre to a
depth of 1 ft; equal to 43,560 ft3 or 325, 851 gal.

Active storage capacity - The total usable storage capacity available
for seasonal or cyclic water storage. It is gross reservoir capacity minus
inactive storage capacity.

Aeration - Any active or passive process by which intimate contact
between air and liquid are assured, generally by spraying liquid in the air,
bubbling air through water, or mechanical agitation of the liquid to promote
surface absorption of air.

Aerobic - Characterizing organisms able to live only in the presence
of air or free oxygen, and conditions that exist only in the presence of air
or free oxygen. Contrast with anaerobic.

Affluent (stream) - A stream or river that flows into a larger one;
a tributary.

Afterbay - A reservoir that regulates fluctuating discharges from a
hydroelectric power plant or a pumping plant.

Aggradation (Aggrade) - A progressive buildup or raising of the channel
bed and floodplain due to sediment deposition. The geologic process by which
streambeds are raised in elevation and flood plains are formed. Aggradation
indicates that stream discharge and/or bed-load characteristics are changing.
Opposite of degradation.

Algae - Microscopic plants that grow in sunlit water containing phosphates,
nitrates, and other nutrients. Algae, like all aquatic plants, add oxygen to
the water and are important in the food chain.

Alluvial - Deposited by running water.

Alluvium - A general term for detrital deposits made by stream processes
on riverbeds, floodplains, and alluvial fans; esp. a deposit of silt or silty
clay laid down during times of flood. The term applies to stream deposits of
recent time. It does not include subaqueous sediments of seas or lakes.

Anabranch - A diverging branch of a river that re-enters the main stream.

Anadromous - Pertaining to fish that spend a part of their life cycle
in the sea and return to freshwater streams to spawn.

Angler-day - The time spent fishing for any part of a day by one person.

Aquaduct - A pipe or conduit made to bring water from a source.

Aquatic ecosystem - Any body of water, such as a stream, lake, or estuary,
and all organisms and nonliving components within it, functioning as a natural
system.

Aquatic habitat - Habitat that occurs in free water.

Aquifer - A body of rock that is sufficiently permeable to conduct
groundwater and to yield economically significant quantities of water to wells
and springs.

Arid - A term describing a climate or region in which precipitation
is so deficient in quantity or occurs so infrequently that intensive agricultural
production is not possible without irrigation.

Armoring - A natural or artificial process where an erosion-resistant
layer of relatively large particles is established on the surface of the streambed
through the removal of finer particles by stream flow. A properly armored streambed
generally resists movement of the bed material at discharges up to approximately "three fourths" bank-full
depth.

Artificial discharge - Addition of surface water to a groundwater reservoir
by human activity, such as putting surface water into spreading basins. See
also groundwater recharge, recharge basin.

Backwater - (1) A small, generally shallow body of water attached to
the main channel, with little or no current of its own, or (2) A condition
in subcritical flow where the water surface elevation is raised by downstream
flow impediments.

Backwater pool - A pool that formed as a result of an obstruction like
a large tree, weir, dam, or boulder.

Bank stability - The ability of a streambank to counteract erosion
or gravitational forces.

Bank-full channel depth - the maximum depth of a channel within a rifle
segment when flowing at a bank-full discharge.

Bank-full channel width - The top surface width of a stream channel
when flowing at a bank-full discharge.

Bank-full discharge - The stream discharge corresponding to the water
stage that first overtops the natural banks. This flow occurs, on average,
about once every 1 or 2 years.

Bank-full width - the width of a river or stream channel between the
highest banks on either side of a stream.

Bar - an accumulation of alluvium (usually gravel or sand) caused by
a decrease in sediment transport capacity on the inside of meander bends or
in the center of an overwide channel.

Barrier - A physical block or impediment to the movement or migration
of fish, such as a waterfall (natural barrier) or a dam (man-made barrier).

Base flow - The sustained portion of stream discharge that is drawn
from natural storage sources, and not affected by human activity or regulation.

Base level - The elevation to which a stream-channel profile has developed.

Bed - The bottom of a channel.

Bed load - Sediment moving on or near the streambed and transported
by jumping, rolling, or sliding on the bed layer of a stream. See also suspended
load.

Bed material - The sediment mixture that a streambed is composed of.

Bed material load - That portion of the total sediment load with sediments
of a size found in the streambed.

Bed roughness - A measure of the irregularity of the streambed as it
contributes to flow resistance. Commonly expressed as a Manning "n" value.

Bed scarp (or nick point) - An abrupt change of grade in the bottom
of a stream channel that moves progressively upstream; the change in grade
forms a waterfall. Also, the location where a streambed is actively eroding
downward to a new base level.

Bed slope - The inclination of the channel bottom, measured as the
elevation drop per unit length of channel.

Benthic invertebrates - Aquatic animals without backbones that dwell
on or in the bottom sediments of fresh or salt water. Examples: clams, crayfish,
and a wide variety of worms.

Benthos - All plants and animals living on or closely associated with
the bottom of a body of water.

Best management practice (BMP) - Conservation measures intended to
minimize or mitigate impacts from a variety of land-use activities.

Biota - All living organisms of a region, as in a stream or other body
of water.

Blowdown - Trees felled at the base by high winds.

Bog - Freshwater wetlands that are poorly drained and characterized
by a buildup of peat.

Boulder - A large substrate particle that is larger than cobble, 256
mm in diameter.

Brackish water - Generally, water containing dissolved minerals in
amounts that exceed normally acceptable standards for municipal, domestic,
and irrigation uses. Considerably less saline than seawater. Also, marine and
estuarine waters with mixohaline salinity (0.5-17.0 ppt due to ocean salts).
Water containing between 500-17,000 parts per million (PPM) total dissolved
solids (TDS). The term brackish water is frequently interchangeable with saline
water. The term should not be applied to inland waters.

Braided channel - A stream characterized by flow within several channels,
which successively meet and divide. Braiding often occurs when sediment loading
is too large to be carried by a single channel.

Buffer strip - A barrier of permanent vegetation, either forest or
other vegetation, between waterways and land uses such as agriculture or urban
development, designed to interrupt and filter out pollution before it reaches
the surface water resource.

Butt end - The bottom end of a cutting taken from a riparian plant
that will root if planted in soil (it is opposite the budding tip's end of
the cutting).

Canopy - A layer of continuous foliage in a forest stand. This most
often refers to the upmost layer of foliage, but it can be used to describe
lower layers in a multistoried stand. Leaves, branches and/or water that provide
shade and cover for fish and wildlife.

Closed basin - A basin whose topography prevents surface outflow of
water. It is considered to be hydrologically closed if neither surface nor
underground outflow of water can occur.

Coarse woody debris (CWD) - Portion of a tree that has fallen or been
cut and left in the woods. Usually refers to pieces at least 20 inches in diameter.

Cobble - Substrate particles that are smaller than boulders and larger
than gravels, and are generally 64-256 mm in diameter. Can be further classified
as small and large cobble.

Confined aquifer - A water-bearing subsurface stratum that is bounded
above and below by formations of impermeable soil or rock.

Confluence - (1) The act of flowing together; the meeting or junction
of two or more streams; also, the place where these streams meet. (2) The stream
or body of water formed by the junction of two or more streams; a combined
flood.

Conifer - A tree belonging to the Gymnospermae, comprising a wide range
of trees that are mostly evergreens. Conifers bear cones (hence, coniferous)
and have needle-shaped or scale-like leaves.

Conjunctive use - The operation of a groundwater basin in combination
with a surface water storage and conveyance system. Water is stored in the
groundwater basin for later use by intentionally recharging the basin during
years of above-average water supply.

Conservation - The process or means of achieving recovery of variable
populations.

Conservation area - Designated land where conservation strategies
are applied for the purpose of attaining a viable plant or animal population.

Conservation strategy - A management plan for a species, group of
species, or ecosystem that prescribes standards and guidelines that, if implemented,
provide a high likelihood that the species, groups of species or ecosystem,
with its full complement of species and processes, will continue to exist well-distributed
throughout a planning area, i.e. a viable population.

Contaminate - To make impure or unclean by contact or mixture.

Contiguous habitat - Habitat suitable to support the life needs of
a species that is distributed continuously across the landscape.

Core area - The area of habitat essential in the breeding, nesting,
and rearing of young, up to the point of dispersal of the young.

Creel census survey - The collection of data concerning the number
of fish caught by sport fishers on a particular stream or in a particular area.

Critical habitat - Under the Endangered Species Act, critical habitat
is defined as(1) the specific areas within a geographic area occupied by a
federally listed species on which are found physical and biological features
essential to the conservation of the species, and that may require special
management considerations or protections; and (2) specific areas outside the
geographic area occupied by a listed species, when it is determined that such
areas are essential for the conservation of the species.

Critical shear stress - The minimum amount of shear stress exerted
by stream currents required to initiate soil particle motion. Because gravity
also contributes to streambank particle movement but not on streambeds, critical
shear stress along streambanks is less than for streambeds.

Crown - the upper part of a tree or other woody plant that carries
the main system of branches and the foliage.

Crown cover - The degree to which the crowns of trees are nearing general
contact with one another.

Cubic feet per second (cfs) - A unit used to measure water flow. One
cubic foot per second is equal to 449 gallons per minute.

Culvert - A buried pipe that allows flows to pass under a road.

Cut bank - The outside bank of a bend, often eroding opposite a point
bar.

Daylight - In the restoration field, a verb that denotes the excavation
and restoration of a stream channel from an underground culvert, covering,
or pipe.

Deadman - A log, block of concrete, rebar, or other object buried in
a stream bank that is used to tie in revetment with cable or chain.

Debris flow - A rapidly moving mass of rock fragments, soil, and mud,
with more than half of the particles being larger than sand size.

Debris torrent - Rapid movement of a large quantity of materials (wood
and sediment) down a stream channel during storms or floods. This generally
occurs in smaller streams and results in scouring of the streambed.

Deciduous - Trees and plants that shed their leaves at the end of
a growing season.

Decomposer - Any of various organisms (as many bacteria and fungi)
that feed on and break down organic substances (such as dead plants and animals).

Decomposition - The breakdown of matter by bacteria and fungi, changing
the chemical makeup and physical appearance of materials.

Deep percolation - the percolation of water through the ground and
beyond the lower limit of the root zone of plants into a groundwater aquifer.

Degradation (degrade) - (1) A progressive lowering of the channel bed
due to scour. Degradation is an indicator that the stream's discharge and/or
sediment load is changing. The opposite of aggradation. (2) A decrease in value
for a designated use.

Dependable supply - The annual average quantity of water that can be
delivered during a drought period.

Depletion - A water use term. The water consumed within a service area
and no longer available as a source of supply. For agriculture and wetlands,
it is evapotranspiration of applied water (ETAW) and evapotranspiration (ET)
of flooded wetlands, plus irrecoverable losses. For urban water use, it is
ETAW (water applied to landscaping or home gardens), sewage effluent that flows
to a salt link, and incidental ET losses. For instream use, it is the amount
of dedicated flow that becomes groundwater and is not available for reuse.

Dike (groin, spur, jetty, deflector, boom) - (1) (Engineering) An embankment
to confine or control water, especially one built along the banks of a river
to prevent overflow of lowlands; a levee. (2) A low wall that can act as a
barrier to prevent a spill from spreading. (3) (Geology) A tabular body of
igneous (formed by volcanic action) rock that cuts across the structure of
adjacent rocks or cuts adjacent rocks.

Discharge - The volume of water passing through a channel during a
given time, usually measured in cubic feet per second.

Discount rate - The interest rate used in evaluating water (and other)
projects to calculate the present value of future benefits and future costs
or to convert benefits and costs to a common time basis.

Dissolved gas concentrations - The amount of chemicals normally occurring
as gases, such as nitrogen and oxygen, that are held in solution in water,
expressed in units such as milligrams of the gas per liter of liquid. Supersaturation
occurs when these solutions exceed the saturation level of the water (beyond
100 percent).

Dissolved organic compounds - Carbon substances dissolved in water.

Dissolved oxygen (DO) - The amount of free (not chemically combined)
oxygen dissolved in water, wastewater, or other liquid, usually expressed in
milligrams per liter, parts per million, or percent of saturation.

Ditch - A long narrow trench or furrow dug in the ground, as for irrigation,
drainage, or a boundary line.

Diversion - The transfer of water from a stream, lake, aquifer, or
other conduit to another watercourse or to the land, as in the case of an irrigation
system.

Diversion channel - (1) An artificial channel constructed around a
town or other point of high potential flood damages to divert floodwater from
the main channel to minimize flood damage. (2) A channel carrying water from
a diversion dam.

Dominant discharge - The channel-forming discharge, which is equivalent
to the bankfull discharge, responsible for the active channel that erodes and
deposits, creates pools, riffles, and meanders. The discharge, in terms of
flood frequency, usually has a return period or recurrence interval of 1.5
to 2 years in natural channels. This represents a flow condition where the
stream flow completely fills the stream channel up to the top of the bank before
overflowing onto the floodplain.

Drainage area - The total surface area upstream of a point on a stream
that drains toward that point. Not to be confused with watershed. The drainage
area may include one or more watersheds.

Drainage basin - The total area of land from which water drains into
a specific river.

Dredging - Removing material (usually sediments) from wetlands or waterways,
usually to make them deeper and wider.

Drought - Generally, the term is applied to periods of less than average
or normal precipitation over a certain period of time sufficiently prolonged
to cause a serious hydrological imbalance resulting in biological losses (impact
flora and fauna ecosystems) and/or economic losses (affecting man). In a less
precise sense, it can also signify nature's failure to fulfill the water wants
and needs of man.

Dry wash - A streambed that carries water only during and immediately
following rainstorms.

Ecology - The study of interrelationships of living organisms to one
another and to their surroundings.

Economic demand - The consumer's willingness and ability to purchase
some quantity of a commodity based on the price of that commodity.

Ecosystem - (1) Recognizable, relatively homogeneous units, including
the organisms they contain, their environment, and all the interactions among
them. (2) Any complex of organisms in an environment considered as a unit for
the purpose of study.

Ecosystem management - A strategy or plan to manage ecosystems to provide
for all associated organisms, as opposed to a strategy or plan for managing
individual species.

Eddy current - A circular current of water, usually resulting from
an obstruction, that develops when the main flow becomes separated from the
bank.

Effluent - (1) Something that flows out or forth, especially a stream
flowing out of a body of water. (2) (Water Quality) Discharged wastewater such
as the treated wastes from municipal sewage plants, brine wastewater from desalting
operations, and coolant waters from a nuclear power plant.

Embankment - An artificial deposit of material that is raised above
the natural surface of the land and used to contain, divert, or store water,
support roads and railways, or for other similar purposes.

Energy dissipation - The loss of kinetic energy of moving water due
to internal turbulence, bottom friction, large rocks, debris, or other obstacles
that impede flow.

Enhancement - Emphasis on improving the value of particular aspects
of water and related land resources.

Environment - The sum of all external influences and conditions affecting
the life and development of an organism or ecological community; the total
social and cultural conditions.

Environmental analysis - An analysis of alternative actions and their
predictable short-term and long-term environmental effects, incorporating physical,
biological, economic, and social considerations.

Environmental assessment (EA) - A systematic analysis of site-specific
activities used to determine whether such activities have a significant effect
on the quality of the human environment and whether a formal environmental
impact statement is required; and to aid an agency's compliance with the National
Environmental Policy Act when no environmental impact statement is necessary.

Environmental impact - the positive or negative effect of any action
upon a given area or source.

Environmental impact statement (EIS) - A formal document to be filed
with the Environmental Protection Agency that considers significant environmental
impacts expected from implementation of a major federal action.

Ephemeral streams - Streams that flow only in direct response to precipitation
and whose channel is at all times above the water table.

Erosion - Wearing away of rock or soil by the gradual detachment of
soil or rock fragments by water, wind, ice, and other mechanical, chemical,
or biological forces.

Estuary - A coastal body of water that is semi-enclosed, openly connected
with the ocean, and mixes with freshwater drainage from land.

Eutrophic - Usually refers to a nutrient-enriched, highly productive
body of water.

Eutrophication - The process of enrichment of water bodies by nutrients
and the subsequent depletion of dissolved oxygen it produces..

Evaporation - The physical process by which a liquid (or a solid) is
transformed to the gaseous state. In hydrology, evaporation is vaporization
that takes place at a temperature below the boiling point.

Evapotranspiration (ET) - The quantity of water transpired (given off),
retained in plant tissues, and evaporated from plant tissues and surrounding
plant surfaces. Quantitatively, it is usually expressed in terms of depth of
water per unit area during a specified period of time.

Evapotranspiration of applied water (ETAW) - the portion of the total
evapotranspiration provided by irrigation.

Failure - Collapse or slippage of a large mass of bank material into
a stream.

Fill - (1) (Geology) Any sediment deposited by any agent such as water
so as to fill or partly fill a channel, valley, sink, or other depression.
(2) (Engineering) Soil or other material placed as part of a construction activity.

Filter fabric - A polypropylene textile used to keep soil separate
from water. Comes in many different forms and is used for constructing roads,
lining ponds, and in many erosion control projects.

Final environmental impact statement (FEIS) - The final report of environmental
effects of proposed action on an area of land. This is required for major federal
actions under Section 102 of the National Environmental Policy Act. It is a
revision of the draft environmental impact statement to include public and
agency responses to the draft.

Flash flood - A sudden flood of great volume, usually caused by a heavy
rain. Also, a flood that crests in a short length of time and is often characterized
by high velocity flows.

Flood insurance rate map (FIRM) - A map used to establish the insurance
rates for structures under the National Flood Insurance Plan.

Floodplain - Land built of sediment that is regularly covered with
water as a result of the flooding of a adjacent stream.

Floodplain (100-year) - The area adjacent to a stream that is on average
inundated once a century.

Flood stage - An above average elevation for the water level at high
flows.

Floodway - A regulatory floodplain under the National Flood Insurance
Program that includes the channel and that portion of the adjacent floodplain
that is required to pass flood flows (normally the one-in-100-year flood) without
increasing the water surface elevation more than a designated height (1 foot
in most areas).

Flow - The amount of water passing a particular point in a stream or
river, usually expressed in cubic feet per second (cfs).

Flow augmentation - Increased flow from release of water from storage
dams.

Fluvial - Migrating between main rivers and tributaries. Of or pertaining
to streams or rivers.

Ford - A shallow place in a body of water, such as a river, where one
can cross by walking or riding on an animal or in a vehicle.

Forebay - A reservoir or pond situated at the intake of a pumping plant
or power plant to stabilize water levels; also, a storage basin for regulating
water for percolation into groundwater basins.

Gabion - A wire basket or cage that is filled with gravel or cobble
and generally used to stabilize streambanks.

Gaging station - A particular site in a stream, lake, reservoir, etc.,
where hydrologic data are obtained.

Gallons per minute (gpm) - A unit used to measure water flow.

Geographic information system (GIS) - A computer system capable of
storing and manipulating spatial data.

Geomorphology - A branch of both physiography and geology that deals
with the form of the earth, the general configuration of its surface, and the
changes that take place due to erosion of the primary elements and the buildup
of erosional debris.

Glide - A section of stream that has little or no turbulence.

Grade control structure - A weir, dam, sill, drop structure, or other
structure used to control erosion in stream channels with steep grades or where
the slope has been destabilized.

Gradient - Vertical drop per unit of horizontal distance.

Grass/forb - Herbaceous vegetation.

Gravel - An unconsolidated natural accumulation of rounded rock fragments,
mostly of particles larger than sand (diameter greater than 2 mm), such as
boulders, cobbles, pebbles, granules, or any combination of these.

Gray water - Wastewater from a household or small commercial establishment
that specifically excludes water from a toilet, kitchen sink, dishwater, or
water used for washing diapers.

Greenbelt - Strip of natural vegetation growing parallel to a stream
that provides wildlife habitat and an erosion and flood buffer zone. This strip
of vegetation also retards rainfall runoff down the bank slope and provides
a root system that binds soil particles together.

Groundwater - Subsurface water and underground streams that can be
collected with wells, or that flow naturally to the earth's surface through
springs.

Groundwater basin - A groundwater reservoir, defined by an overlying
land surface and the underlying aquifers that contain water stored in the reservoir.
In some cases, the boundaries of successively deeper aquifers may differ and
make it difficult to define the limits of the basin.

Groundwater flow - Water that moves through the subsurface soil and
rocks.

Groundwater overdraft - The condition of a groundwater basin in which
the amount of water withdrawn by pumping exceeds the amount of water that recharges
the basin over a period of years during which water supply conditions approximate
average.

Groundwater prime supply - Long-term average annual percolation into
major groundwater basins from percolation into major groundwater basins from
precipitation falling on the land and from flows in rivers and streams.

Groundwater recharge - Increases in groundwater storage by natural
conditions or by human activity. See also artificial recharge.

Groundwater storage capacity - The space or voids contained in a given
volume of soil and rock deposits.

Groundwater table - The upper surface of the zone of saturation, except
where the surface is formed by an impermeable body.

Habitat - The local environment in which organisms normally live and
grow.

Habitat conservation plan (HCP) - An agreement between the Secretary
of the Interior and either a private entity or a state that specifies conservation
measures that will be implemented in exchange for a permit that would allow
taking of a threatened or endangered species.

Habitat diversity - The number of different types of habitat within
a given area.

Habitat fragmentation - The breaking up of habitat into discrete islands
through modification or conversion of habitat by management activities.

Hardpan - A layer of nearly impermeable soil beneath a more permeable
soil, formed by natural chemical cementing of the soil particles.

Hard water - Water high in multivalent cations, such as calcium and
magnesium. This type of water does not lather easily when used with soap and
forms a scale in containers when allowed to evaporate.

Hatch box - A device used to incubate relatively small numbers of eggs.
The hatch box is usually located adjacent to a stream, which supplies the box
with water.

Headcut - A break in the slope at the top of a gully or section of
a gully that forms a "waterfall" which in turn causes the underlying soil to
erode and the gully to expand uphill.

Headcutting - The action of a bedscarp or headward erosion of a locally
steep channel or gully.

Headwater - Referring to the source of a stream or river.

Heavy metals - Metallic elements with high atomic weights, e.g., mercury,
chromium, cadmium, arsenic, and lead. They can damage living things at low
concentrations, and tend to accumulate in the food chain.

Hungry water - Clear water minus its expected suspended sediment load,
usually released from an impoundment that has excess energy, which erodes sediment
from the downstream channel.

Hydraulic gradient - The slope or the water surface. See also streambed
gradient.

Hydraulic radius - The cross-sectional area of a stream divided by
the wetted perimeter.

Hydric - Wet.

Hydrograph - A curve showing stream discharge over time.

Hydrologic balance - An accounting of all water inflow to, water outflow
from, and changes in water storage within a hydrologic unit over a specified
period of time.

Hydrologic region - A study area, consisting of one or more planning
subareas, that has a common hydrologic character.

Hydrologic unit - A distinct watershed or river basin defined by an
eight-digit code.

Hydrology - The scientific study of water of the earth, its occurrence,
circulation, and distribution, its chemical and physical properties, and its
interaction with the environment, including its relationship to living things.

Hyporheic zone - The area under the stream channel and floodplain
where groundwater and the surface waters of a stream are exchanged freely.

Impermeable channel - A material that has properties preventing movement
of water through it. Nonporous.

Incised river (channel) - A river that erodes its channel by a process
of degradation to a lower base level than existed previously or is consistent
with the current hydrology.

Infiltration (soil) - The movement of water through the soil surface
into the soil.

Inflow - Water that flows into a stream, lake, reservoir, or Forebay
during a specified period.

Instream cover - The layers of vegetation, like trees, shrubs, and
overhanging vegetation, that are in the stream or immediately adjacent to the
wetted channel.

Instream flows - (1) Portion of a flood flow that is contained by the
channel. (2) A flow or flow regime needed to maintain ecological health in
a river/stream.

Instream use - Use of water that does not require diversion from its
natural watercourse. For example, the use of water for navigation, recreation,
fish and wildlife, aesthetics, and scenic enjoyment.

Intermittent stream - Any nonpermanent flowing drainage feature having
a definable channel and evidence of scour or deposition. This includes what
are sometimes referred to as ephemeral streams if they meet these two criteria.

Invertebrate drift - Stream and terrestrial invertebrates that float
with the current.

Irrigation diversion - Generally, a ditch or channel that deflects
water from a stream channel for irrigation purposes.

Irrigation efficiency - The efficiency of water application and use.
Computed by dividing evapotranspiration of applied water by applied water and
converting the result to a percentage. Efficiency can be computed at three
levels: farm, district, or basin.

Irrigation return flow - applied water that is not transpired, evaporated,
or deep-percolated into a groundwater basin but returns to a surface water
supply.

Key watershed - As defined by National Forest and Bureau of Land Management
District fish biologists, a watershed containing (1) habitat for potentially
threatened species or stocks of anadromus salmonids or other potentially threatened
fish, or (2) greater than six square miles with high-quality water and fish
habitat.

Keyway (key) - The notch excavated into the side of a gully or stream
to anchor a check dam or other structure.

Lake - An inland body of standing water deeper than a pond, an expanded
part of a river, a reservoir behind a dam.

Landscape - A heterogenous land area with interacting ecosystems that
are repeated in similar form throughout.

Landscape diversity - The size, shape, and connectivity of different
ecosystems across a large area.

Landscape features - The land, water, vegetation, and structures that
compose the characteristic landscape.

Landslide - a movement of earth mass down a steep slope.

Large woody debris (LWD) - Pieces of naturally occurring wood larger
than 10 ft long and 6 in. in diameter, in a stream channel.

Leaching - The flushing of minerals or pollutants from soil or other
material by the percolation of applied water.

Leaf area index - A measure of the total area of leaves, twigs, stems,
etc. relative to the area of the canopy in a forest.

Levee - An embankment constructed to prevent a river from overflowing
(flooding).

Lifts - Layers of loose soil. Used to specify how much loose soil should
be laid down at a time before it must be compacted or wrapped in geotextile
fabric.

Limiting factor - A requirement such as food, cover, or another, physical,
chemical, or biological factor that is in shortest supply with respect to all
resources necessary to sustain life and thus "limits" the size or retards production
of a population.

Limnology - The study of life in lakes, ponds, and streams.

Loading - The influx of pollutants to a selected water body.

Longitudinal profile - A graphic presentation of elevation vs. distance;
in channel hydraulics it is a plot of water surface elevation against upstream
to downstream distance.

Macroinvertebrate - Invertebrates visible to the naked eye, such as
insect larvae and crayfish.

Macrophytes - Aquatic plants that are large enough to be seen with
the naked eye.

Main stem - The principal channel of a drainage system into which other
smaller streams or rivers flow.

Mass movement - The downslope movement of the earth caused by gravity.
Includes but is not limited to landslides, rock falls, debris avalanches, and
creep. It does not however, include surface erosion by running water. It may
be caused by natural disturbances (e.g., earthquakes or fire events) or human
disturbances (e.g., mining or road construction).

Maximum contaminant level (MCL) - The highest concentration of a constituent
in drinking water permitted under federal and State Safe Drinking Water Act
regulations.

Mean annual discharge - Daily mean discharge averaged over a period
of years. Mean annual discharge generally fills a channel to about one-third
of its bank-full depth.

Mean velocity - The average cross-sectional velocity of water in a
stream channel. Surface values typically are much higher than bottom velocities.
May be approximated in the field by multiplying the surface velocity, as determined
with a float, times 0.8.

Meander - The winding of a stream channel, usually in an erodible
alluvial valley. A series of sine-generated curves characterized by curved
flow and alternating banks and shoals.

Meander amplitude - The distance between points of maximum curvature
of successive meanders of opposite phase in a direction normal to the general
course of the meander belt, measured between centerlines of channels.

Meander belt width - The distance between lines drawn tangential to
the extreme limits of fully developed meanders. Not to be confused with meander
amplitude.

Meander length - The lineal distance downvalley between two corresponding
points of successive meanders of the same phase.

Mesic - Moderately wet.

Milligrams per liter (mg/l) - the weight in milligrams of any substance
dissolved in one liter of liquid; nearly the same as parts per million by weight.

Mineralization - The process whereby concentrations of minerals, such
as salts, increase in water, often a natural process resulting from water dissolving
minerals found in rocks and soils through which it flows.

Moisture stress - A condition of physiological stress in a plant caused
by lack of water.

Morphology - the form, shape, or structure of a stream or organism.

Multipurpose project - A project designed to serve more than one purpose.
For example, one that provides water for irrigation, recreation, fish and wildlife,
and, at the same time, controls floods or generates electric power.

National Pollutant Discharge Elimination System (NPDES) - A provision
of Section 402 of the Federal Clean Water Act of 1972 that established a permitting
system for discharges of waste materials to watercourses.

Natural flow - The flow past a specified point on a natural stream
that is unaffected by stream diversion, storage, import, export, return flow,
or change in use caused by modifications in land use.

Net water demand (net water use) - The amount of water needed in a
water service area to meet all requirements. It is the sum of evapotranspiration
of applied water (ETAW) in an area, the irrecoverable losses from the distribution
system, and the outflow leaving the service area; does not include reuse of
water within a service area (such as reuse of deep-percolated applied water
or use of tailwater).

Nick point - The point at which a stream is actively eroding the streambed
to a new base level.

Non-cohesive soil - Soil particles that have no natural resistance
to being pulled apart at their point of contact, for example, silt, sand, gravel.

Non-point source pollution (NPS) - Pollution that does not originate
from a clear or discrete source.

Normalization - The mathematical manipulation of a variable to allow
comparisons with an otherwise different variable.

Normalized demand - The process of adjusting actual water use in a
given year to account for unusual events such as dry weather conditions, government
interventions for agriculture, rationing programs, or other irregularities.

Nutrient depletion - Detrimental changes at a site in the total amount
of nutrients and/or their rates of input, uptake, release, movement, transformation,
or export.

Off-channel area - Any relatively calm portion of a stream outside
of the main flow.

Off-site enhancement - The improvement in conditions for fish and wildlife
species away from the site or development activities that may have detrimental
effects on fish and/or wildlife, as part or total compensation for those effects.

Overbank flow - Water flow over the top of the bankfull channel onto
the floodplain.

Outfall - The mouth or outlet of a river, stream, lake, drain or sewer.

Oxbow - An abandoned meander in a river or stream, caused by cutoff.
Used to describe the U-shaped bend in the river or the land within such a bend
of a river.

Per capita water use - The water produced by or introduced into the
system of a water supplier divided by the total residential population; normally
expressed in gallons per capita per day (gpcd).

Perched groundwater - Groundwater supported by a zone of material of
low permeability located above an underlying main body of groundwater with
which it is not hydrostatically connected.

Percolation - The downward movement of water through the soil or alluvium
to a groundwater table.

Perennial streams - Streams that flow continuously.

Perennial yield - The maximum quantity of water that can be annually
withdrawn from a groundwater basin over a long period of time (during which
water supply conditions approximate average conditions) without developing
an overdraft condition. Sometimes referred to as sustained yield.

Permeability - The capability of soil or other geologic formations
to transmit water.

pH - The negative logarithm of the molar concentration of the hydrogen
ion, or, more simply acidity.

Phytoplankton - Minute plants, usually algae, that live suspended in
bodies of water and that drift about because they are too small or too weak
to swim effectively against the current.

Piping - The process by which water forces an opening around or through
a supposedly sealed structure, such as a check dam or levee. As water flows
through, the opening usually grows larger and the water carries awat sediment
or levee material.

Point bar - The convex side of a meander bend that is built up due
to sediment deposition.

Point Source (PS) - (1) A stationary or clearly identifiable source
of a large individual water or air pollution emission, generally of an industrial
nature. (2) Any discernible, confined, or discrete conveyance from which pollutants
are or may be discharged, including (but not limited to) pipes, ditches, channels,
tunnels, conduits, wells, containers, rolling stock, concentrated animal feeding
operations, or vessels. Point source is also legally and more precisely defined
in federal regulations. Contrast with non-point source (NPS) pollution.

Pollutant - (1) Something that pollutes, especially a waste material
that contaminates air, soil, or water. (2) Any solute or cause of change in
physical, chemical, or biological properties that renders water unfit for a
given use.

Pollution (of water) - The alteration of the physical, chemical, or
biological properties of water by the introduction of any substance into water
that adversely affects any beneficial use of water.

Pond - A body of water smaller than a lake, often artificially formed.

Pool - A reach of a stream that is characterized by deep, low-velocity
water and a smooth surface.

Pool/riffle ratio - The ratio of surface area or length of pools to
the surface area or length of riffles in a given stream reach; frequently expressed
as a relative percentage of each category. Used to describe fish habitat rearing
quality.

Probability of exceedence - The probability that a random flood will
exceed a specified magnitude in a given period of time.

Pumped storage project - A hydroelectric power plant and reservoir
system in which water released for generating energy during peak load periods
is stored and pumped back into the upper reservoir, usually during periods
of reduced power demand.

Rapid - A reach of stream that is characterized by small falls and
turbulent, high-velocity water.

Rapid drawdown - Lowering the elevation of water against a bank faster
than the bank can drain, leaving a pressure imbalance that may cause the bank
to fail.

Reach - A section of stream between two defined points.

Rearing habitat - Areas in rivers or streams where juvenile fish find
food and shelter to live and grow.

Rearing pond - An artificial impoundment in which juvenile fish are
raised prior to release into the natural habitat.

Recharge basin - A surface facility, often a large pond, used to increase
the percolation of surface water into a groundwater basin.

Recreational rivers - Rivers or sections of rivers that are readily
accessible by road or railroad, that may have some development along their
shoreline, and that may have undergone some impoundment or diversion in the
past.

Recreation-day - Participation in a recreational activity, such as
skiing, biking, hiking, fishing, boating, and/or camping, for any part of a
day by one person.

Recycled water - Urban watershed that becomes suitable, as a result
of treatment, for a specific direct beneficial use. See also water recycling.

Reforestation - The natural or artificial restocking of an area with
forested trees.

Regime theory - A theory of channel formation that applies to streams
that make a part of their boundaries from their transported sediment load and
a portion of their transported sediment load from their boundaries. Channels
are considered in regime or equilibrium when bank erosion and bank formation
are equal.

Restoration - The return of an ecosystem to a close approximation of
its condition prior to disturbance.

Return flow - The portion of withdrawn water not consumed by evapotranspiration
or system losses that returns to its source or to another body of water.

Reuse - The additional use of previously used water.

Revetment - A facing of stone, bags, blocks, pavement, etc., used
to protect a bank against erosion.

Riffle - A reach of stream that is characterized by shallow, fast-moving
water broken by the presence of rocks and boulders.

Rift - A shallow or rocky place in a stream, forming either a ford
or a rapid.

Rill erosion - Removal of soil particles from a bank slope by surface
runoff moving through relatively small channels. The water collecting from
these small channels may then concentrate into a larger channel downhill to
form the start of a gully.

Riparian area - An area of land and vegetation adjacent to a stream
that has a direct effect on the stream. This includes woodlands, vegetation,
and floodplains.

Riparian habitat - The aquatic and terrestrial habitat adjacent to
streams, lakes, estuaries, or other waterways.

Riparian - Located on the banks or a stream or other body of water.

Riparian vegetation - The plants that grow adjacent to a wetland area
such as a river, stream, reservoir, pond, spring, marsh, bog, meadow, etc.,
and that rely upon the hydrology of the associated water body.

Ripple - (1) A specific undulated bed form found in sand bed streams.
(2) Undulations or waves on the surface of flowing water.

Riprap - Rock or other material with a specific mixture of sizes referred
to as a "gradation" used to stabilize streambanks or riverbanks from erosion
or to create habitat features in a stream.

River channels - Large natural or artificial open streams that continuously
or periodically contain moving water, or which form a connection between two
bodies of water.

River miles - Generally, miles from the mouth of a river to a specific
destination or, for upstream tributaries, from the confluence with a main river
to a specific destination.

River reach - Any defined length of river.

River stage - The elevation of the water surface at a specified station
above some arbitrary zero datum (level).

Riverine - Relating to, formed by, or resembling a river including
tributaries, streams, brooks, etc.

Riverine habitat - The aquatic habitat within streams and rivers.

Rock - A naturally formed mass of minerals.

Rootwad - The mass of roots associated with a tree adjacent to or in
a stream that provides refuge for fish and other aquatic life.

Run (in stream or river) - A reach of stream characterized by fast-flowing,
low turbulence water.

Runoff - Water that flows over the ground and reaches a stream as a
result of rainfall or snowmelt.

Salinity - The concentration of mineral salts dissolved in water. Salinity
may be measured by weight (total dissolved solids), electrical conductivity,
or osmotic pressure. Where seawater is known to be the major source of the
salt, salinity is often used to refer to the concentration of chlorides in
the water.

Salinity intrusion - The movement of saltwater into a body of freshwater.
It can occur in either surface water or groundwater bodies.

Salt marsh - Saltwater wetlands that occur along many coasts.

Saltwater barrier - A physical facility or method of operation designed
to prevent the intrusion of saltwater into a body of freshwater.

Sand - Small substrate particles, generally from 0.6 to 2.0 mm in diameter.
Sand is larger than silt and smaller than gravel.

Scenic rivers - Rivers or sections of rivers that are free of impoundments,
with shoreline and watersheds still largely primitive, and shorelines largely
undeveloped, but accessible in places by roads.

Scour - the erosive action of running water in streams, which excavates
and carries away material from the bed and banks. Scour may occur in both earth
and solid rock material and can be classed as general, contraction, or local
scour.

Seasonal application efficiency (SAE) - The sum of evapotranspiration
of applied water and leaching requirement divided by the total applied water,
expressed as a percentage: SAE=(ETAW+LR)/AW.

Secchi depth - A relatively crude measurement of the turbidity (cloudiness)
of surface water. The depth at which a Secchi disc (disk), which is about 10-12
in. in diameter and with a black and white pattern, can no longer be seen.

Secchi disc - A circular plate, generally about 10-12 in (25.4-30.5
cm) in diameter, used to measure the transparency or clarity of water by noting
the greatest depth at which it can be visually detected. Its primary use is
in the study of lakes.

Secondary treatment - In sewage, the biological process of reducing
suspended, colloidal, and dissolved organic matter in effluent from primary
treatment systems. Secondary treatment usually involves the use of trickling
filters or the activated sludge process.

Sediment - Soil or mineral material transported by water or wind and
deposited in streams or other bodies of water.

Sediment load - The soil particles transported through a channel by
stream flow.

Seepage - The gradual movement of a fluid into, through, or from a
porous medium.

Setback - Denotes the positioning of a levee or structure in relationship
to a stream bank. A setback levee is placed a substantial distance from a stream
to allow it to meander without consequences to the levee and to accommodate
a floodplain that can store and convey flood flows. A setback regulation of
a certain number of feet can be a requirement for the placement of urban buildings
away from a stream channel bank.

Shear - Force parallel to a surface as opposed to directly on the surface.
An example of shear would be the Tractive force that removes particles from
a stream bank as flow moves over the surface of the slope; a floating log that
directly strikes the bank would not be a shear force.

Sheet erosion - The removal by surface runoff of a fairly uniform layer
of soil from a bank slope from "sheet flow" or runoff that flows over the ground
surface as a thin, even layer not concentrated in a channel.

Soft water - Water that contains low concentrations of multivalent
cations, such as calcium and magnesium. This type of water does not precipitate
soaps and detergents.

Soil bioengineering - Also referred to as biotechnical slope protection.
Involves the use of live and dead woody cuttings and poles or posts collected
from native plants to revegetate watershed slopes and stream banks. The cuttings,
posts, and vegetative systems composed of bundles, layers, and mats of the
cuttings and posts provide structure, drains, and vegetative cover to repair
eroding and slumping slopes.

Spawning - The depositing and fertilizing of eggs (or roe) by fish
and other aquatic life.

Spillway - A channel for reservoir overflow.

Stable channel - A stream channel with the right balance of slope,
planform, and cross section to transport both the water and sediment load without
net long-term bed or bank sediment deposition or erosion throughout the stream
segment.

Stone - Rock or rock fragments used for construction.

Stream - A general term for a body of water flowing by gravity; natural
watercourse containing water at least part of the year. In hydrology, the term
is generally applied to the water flowing in a natural narrow channel as distinct
from a canal.

Stream bank - The side slopes of an active channel between which the
streamflow is normally confined.

Stream channel - A long narrow depression shaped by the concentrated
flow of a stream and covered continuously or periodically by water.

Stream gradient - A general slope or rate of change in vertical elevation
per unit of horizontal distance of the bed, water surface, or energy grade
of a stream.

Stream morphology - The form and structure of streams.

Stream order - A hydrologic system of stream classification. Each small
unbranched tributary is a first-order stream. Two first-order streams join
to make a second-order stream. A third-order stream has only first and second-order
tributaries, and so forth.

Stream reach - An individual segment of stream that has beginning and
ending points defined by identifiable features such as where a tributary confluence
changes the channel character or order.

Streambank erosion - The removal of soil from streambanks by flowing
water.

Streambank protection works - Structure placed on or near a distressed
stream bank to control bank erosion or prevent failure.

Streambank stabilization - The lining of streambanks with riprap, matting,
etc., or other measures intended to control erosion.

Streambed - (1) The unvegetated portion of a channel boundary below
the baseflow level. (2) The channel through which a natural stream of water
runs or used to run, as a dry streambed.

Streamflow - The rate at which water passes a given point in a stream
or river, usually expressed in cubic feet per second (cfs).

Stream power - Directly related to the sediment transport rates of
a stream and measured as the loss of potential energy per unit length of stream
channel. It refers to the ability of a stream to do work.

Substrate - (1) The composition of a streambed, including either mineral
or organic materials. (2) Materials that forms an attachment medium for organisms.

Subsurface drainage - Rainfall that is not evapotranspirated or does
not become surface runoff.

Superfund list - A list of the hazardous waste disposal sites most
in need of cleanup. The list is updated annually by the U.S. Environmental
Protection Agency (EPA) based primarily on how a site scores using the Hazard
Ranking System. Also referred to as the National Priorities List (NPL).

Supply augmentation - Alternative water management programs such as
conjunctive use, water banking, or water project facility expansion that increase
supply.

Surface erosion - The detachment and transport of soil particles by
wind, water, or gravity. Or a group of processes whereby soil materials are
removed by running water, waves and currents, moving ice, or wind.

Surface supply - Water supply from streams, lakes, and reservoirs.

Surface water - All water whose surface is naturally exposed to the
atmosphere, for example, rivers, lakes, reservoirs, ponds, streams, impoundments,
seas, estuaries, etc., and all springs, wells, or other collectors directly
influenced by surface water.

Surplus water - Developed water supplies in excess of contract entitlement
or apportioned water.

Suspended sediment (load) - Sediment suspended in a fluid by the upward
components of turbulent currents, moving ice, or wind.

Suspended sediment load - That portion of a stream's total sediment
load that is transported within the body of water and has very little contact
with the streambed.

Swale - Small depressions, natural or artificial, that carry water
only after a rainfall.

Tailwater - (1) The area immediately downstream of a spillway. (2)
Applied irrigation water that runs off the end of a field.

Terrace - An abandoned floodplain that is located at a higher elevation
than the current active floodplain.

Tertiary treatment - In sewage, the additional treatment of effluent
beyond that of secondary treatment to obtain a very high quality of effluent
for reuse.

Texture - Refers to relative proportions of clay, silt, and sand in
soil.

Thalweg - (1) The lowest thread along the axial part of a valley or
stream channel. (2) A subsurface, groundwater stream percolating beneath and
in the general direction of a surface stream course or valley. (3) The middle,
chief, or deepest part of a navigable channel or waterway.

Tidal flats - Saltwater wetlands that are characterized by mud or sand
and daily tidal fluctuations.

Toe - The break in slope at the foot of a stream bank where the bank
meets the bed.

Top of bank - The break in slope between the bank and the surrounding
terrain.

Total dissolved solids (TDS) - A quantitative measure of the residual
minerals dissolved in water that remain after evaporation of a solution. Usually
expressed in milligrams per liter. See also salinity.

Trash rack - A barrier placed at the upstream end of a culvert to trap
debris but allow water to flow through.

Tractive force - The drag on a streambed or bank caused by passing
water, which tends to pull soil particles along with the streamflow.

Transpiration - An essential physiological process in which plant tissues
give off water vapor to the atmosphere.

Tributary - A stream that flows into another stream, river, or lake.

Turbidity - A measure of the content of suspended matter that interferes
with the passage of light through the water or in which visual depth is restricted.
Suspended sediments are only one components of turbidity.

Velocity - In this concept, the speed of water flowing in a watercourse,
such as a river.

Viscosity - A measure of the resistance of a fluid to flow. For liquids,
viscosity increases with decreasing temperature.

Visitor-day - See recreation-day.

Vortex rocks - Rocks placed in a streambed to help direct flows for
the formation of meanders and creation of riffles and pools. The rocks are
so named for their ability to contribute to sediment transport through the
channel.

Wash - (1) To carry, erode, remove, or destroy by the action of moving
water. To be carried away, removed, or drawn by the action of water. Removal
or erosion of soil by the action of moving water. (2) A deposit of recently
eroded debris. (3) Low or marshy ground washed by tidal waters. A stretch of
shallow water. (4) (Western United States) The dry bed of a stream, particularly
a watercourse associated with arid environments and are characterized by large,
high-energy discharges with high bed-material load transport. Washes are often
intermittent and their beds sparsely vegetated. (5) Turbulence in air or water
caused by the motion or action of an oar, propeller, jet, or airfoil.

Washout - (1) Erosion of a relatively soft surface, such as a roadbed,
by a sudden gush of water, as from a downpour or floods. (2) A channel produced
by such erosion.

Wastewater - The used water, liquid waste, or drainage from a community,
industry, or institution.

Water conservation - Reduction in applied water due to more efficient
water use such as implementation of Urban Best Management Practices or Agricultural
Efficient Water Management Practices. The extent to which these actions actually
create a savings in water supply depends on how they affect net water use and
depletion.

Water demand schedule - A time distribution of the demand for prescribed
quantities of water for specified purposes. It is usually a monthly tabulation
of the total quantity of water that a particular water user intends to use
during a specified year.

Waterfall - A sudden, nearly vertical drop in a stream, as it flows
over rock.

Water pollution - Generally, the presence in water of enough harmful
or objectionable material to damage the water quality.

Water quality - A term used to describe the chemical, physical, and
biological characteristics of water, usually in respect to its suitability
for a particular purpose.

Water recycling - the treatment of urban wastewater to a level rendering
it suitable for a specific, direct, beneficial use.

Water right - A legally protected right to take possession of water
occurring in a natural waterway and to divert that water for beneficial use.

Water table -See groundwater table.

Water year - A continuous 12-month period for which hydrologic records
are compiled and summarized.

Water yield - The quantity of water derived from a unit area of watershed.

Watershed - An area of land whose total surface drainage flows to a
single point in a stream.

Watershed management - the analysis, protection, development, operation,
or maintenance of the land, vegetation, and water resources of a drainage basin
for the conservation of all its resources for the benefit of its residents.

Watershed project - A comprehensive program of structural and nonstructural
measures to preserve or restore a watershed to good hydrologic condition. These
measures may include detention reservoirs, dikes, channels, contour trenches,
terraces, furrows, gully plugs, revegetation, and possibly other practices
to reduce flood peaks and sediment production.